The external lights mounted to a vehicle are some of its most important safety equipment. Marker lights, which are turned on at night or in low-visibility situations, provide a distinct indication of the presence of the vehicle, and of the exact nature of the vehicle; car, small- or medium-sized truck, or large tractor-trailer combination. Stop, backup, and turn lights, which are selectively illuminated, are activated whenever the vehicle on which they are mounted undergoes, or is about to undergo, a corresponding change of motion. These lights, in combination with the marker lights, enable motorists, and others in the vicinity of a vehicle, to quickly comprehend the size, speed, and direction of a vehicle, as well as any changes in its speed and direction, so that appropriate action can be taken in order to avoid accidents.
While marker lights and other external lights have proved to be necessary safety tools, to date, it has been troublesome to mount such lights to the outside of some vehicles that constantly vibrate, such as heavy trucks and the like. This is because most of these light assemblies include a filament-type light bulb. The movement of the vehicle's vibration is often transferred directly to the light bulb, where it first fatigues and then breaks the thin, fragile filament. Moreover, many of these vehicles are operated in relatively cold environments. Prior to their energization, bulb filaments can be at or near the temperature of the surrounding environment. The energization of the filament quickly heats it and the adjacent posts to which it is attached. This rapid warming further fatigues both the filaments and the posts making them less able to withstand the stress imposed as a result of the vehicle's vibration. Consequently, the bulbs mounted in these assemblies have been known to burn out with high regularity.
One method used to reduce the rate at which these bulbs burn out has been to install them in environmentally hardened lamp assemblies. These assemblies typically include some type of shock-absorbing member for holding the bulb to minimize the shock to which it would otherwise be exposed. There is also usually a mechanical coupling for establishing a conductive link between the bulb and the vehicle's power supply system; this coupling is designed to maintain the connection in the event the bulb moves relative to the rest of the vehicle. These assemblies may also be constructed with relatively thick walls that serve to insulate the bulb elements therein to reduce the rate at which their temperature falls to that of the ambient environment.
While these lamp assemblies have served to increase the useful lifetime of the light bulbs with which they are used, they do have some drawbacks. These assemblies tend to have numerous components, which have made them expensive to install. Moreover, the components, in addition to being numerous, are often quite small. The disassembly and reassembly required to remove and replace a light bulb installed in one of these assemblies are frequently complicated, time-consuming tasks. Still another disadvantage of these assemblies is that in extremely cold environments their utility decreases. This is because in these environments the shock-absorbing members of these assemblies lose some of their flexibility. This reduces the assemblies' overall capabilities of minimizing shock. Moreover, in cold environments, regardless of the insulation offered by these assemblies, if a light is deenergized for a long enough period of time, the temperature of the filament and the adjacent components will fall to ambient levels. Upon energization, the filament and adjacent components will be rapidly heated and subjected to thermal shock not much different from that to which bulbs not similarly housed are exposed.